I deal with osteoarthritis and thankfully not rheumatoid arthritis which I know can be much worse. The help offered above is good especially if at all possible a fitter who you believe best understands your limitations and concerns, worth a lot of conversation if you have multiple possible fitters. On weight, while never being a weight weenie and now 70 have found that my +20# bikes are not getting time, not sure it has anything to do with the arthritis, climbing, keeping up with groups, etc., might just enjoy the ride more.